Devices and methods for controlling and indicating the length of an interventional element

ABSTRACT

Devices and methods are provided for controlling and indicating the deployed length of an interventional element on an interventional catheter. The interventional element may be a stent or series of stents, a balloon, or any other interventional element for which length control is necessary or desirable. Devices for controlling the length of the interventional element include gear driven actuators, motors, and other mechanisms. Devices for indicating length of an interventional element to the user include sensors, detents, visual displays and other mechanisms providing visual, audible, and tangible indications of length to the user. The control and indication devices preferably work in tandem to enable highly precise adjustment of interventional element length.

BACKGROUND OF THE INVENTION

The present invention relates generally to interventional catheters andprostheses, and more specifically to catheters and prostheses fortreatment of vascular diseases, including coronary artery disease andperipheral vascular disease, as well as diseases of other body lumenssuch as the biliary tract, fallopian tubes, urinary and digestivetracts, and other structures.

Balloon angioplasty and stenting are widely used in the treatment ofcoronary artery disease and peripheral vascular disease. In coronaryartery disease, one or more coronary blood vessels become narrowed orclosed due to the buildup of stenotic plaques on the arterial wall. Thisblocks blood flow to the heart muscle, potentially causing myocardialinfarction. Such narrowing can also occur in peripheral blood vesselssuch as the carotids, femorals, iliacs and other arteries, blocking theblood supply to other vital tissues and organs.

Balloon angioplasty involves the use of a long flexible catheter havinga balloon at its distal tip. The catheter is inserted into a peripheralartery such as the femoral and advanced transluminally into the diseasedartery. The balloon is inflated within the narrowed portion of thevessel, thereby expanding the vascular lumen and restoring normal bloodflow.

In some cases, however, balloon angioplasty alone is inadequate to treatvascular disease due to restenosis, the renarrowing of the arteryfollowing angioplasty. Stents have been developed to provide anintravascular frame or scaffold to maintain patency of the vascularlumen after it has been expanded. Stents are small tubular prosthesesdesigned to be advanced to the treatment site in a collapsedconfiguration using an elongated delivery catheter. The stents are thenexpanded at the treatment site into engagement with the vessel wall tomaintain vascular patency.

Stents may be either self-expanding or balloon expandable.Self-expanding stents are made of a shape memory material such asNitinol and can be delivered in a compressed state within the tip of thedelivery catheter and allowed to resiliently expand upon release fromthe delivery catheter. Balloon expandable stents are made of a malleablemetal and are mounted to a balloon on the delivery catheter. Whenpositioned at the treatment site, the balloon is inflated to expand thestent into engagement with the vessel.

Stents, however, have also suffered from the problem of restenosis.Restenosis rates with conventional coronary stents have ranged from30-40%. The causes of such restenosis are not fully understood. However,it is believed that restenosis may be caused in some cases by theexcessive stiffness of current stents and their inability to conform tovascular curves, shapes, dimensional changes, and movements. Thisproblem is particularly acute with longer lesions, which may extend overcurved and tapered sections of a vessel and may be subject tonon-uniform movements along their lengths.

The need has thus been demonstrated for highly flexible stents that maybe used to treat long, curved, and tapered vascular regions. Inco-pending U.S. patent application Ser. No. 10/637,713, filed Aug. 8,2003, entitled “Apparatus and Methods for Delivery of VascularProstheses (Attorney Docket No. 21629-000340), the full disclosure ofwhich is incorporated herein by reference, highly flexiblemulti-segmented stents and associated delivery devices are disclosedthat enable the treatment of long, curved or tapered vascular lesions.The disclosed delivery devices enable the selective deployment of one ormore stent segments at a treatment site to allow the user to customizestent length in situ. Moreover, the device can be repositioned atmultiple vascular sites to deploy a plurality of stents of variouslengths.

Other custom-length stents and delivery devices are described inco-pending U.S. patent application Ser. No. 10/624,451, filed Jul. 21,2003, entitled “Apparatus and Methods for Delivery of MultipleDistributed Stents,” (Attorney Docket No. 21629-000400), which is alsoincorporated herein by reference. This application describes separablestent segments as well as continuous prosthesis structures configured asbraids or coils that allow the user to pay out a selected length of theprosthesis structure and deploy it into the vessel at one or moretreatment sites.

Variable length angioplasty devices have also been proposed. Forexample, U.S. Pat. No. 5,246,421 to Saab discloses angioplasty cathetershaving an elongated balloon and an external sheath that is axiallyslidable relative to the balloon. The sheath can be retracted to exposea selected length of the balloon for expansion at a treatment site. Thecatheter can then be repositioned and another length of balloon exposedto treat one or more additional sites.

While such custom-length stents and angioplasty catheters have showngreat promise, there remains a need for improved ways of controlling andproviding indication of balloon and stent length in such devices.Conventional angioplasty and stenting procedures rely upon the use offluoroscopy to visualize the location and operation of catheters andprostheses. However, fluoroscopy often fails to provide the clarity,resolution, and precision that are required for the accurate control ofstent or balloon length, which in many cases must be controlled within afew millimeters. Moreover, even if visualization were adequate, the useris left to control stent or balloon length by manually manipulating theassociated catheters, an operation not well-suited to highly precisecontrol.

SUMMARY OF THE INVENTION

The invention provides devices and methods for controlling andindicating the length of an interventional element on a medical devicesuch as a catheter. The devices and methods facilitate accurate controlof the working or deployed length of an interventional element byproviding highly precise and ergonomic mechanisms for adjusting thelength, and by providing indication devices to give the user accurateindications of the length in real time. The types of interventionalelements to which the invention may be applied are many, but inpreferred embodiments include stents and balloons for the treatment ofvascular disease.

In a first aspect of the invention, an interventional catheter comprisesan elongated flexible shaft having a distal end and a proximal end, andan interventional element at the distal end, the interventional elementhaving an adjustable length. An actuator is disposed near the proximalend for adjusting the length of the interventional element; and anindication device is disposed near the proximal end for indicating thelength to a user. In an exemplary embodiment, the interventional elementcomprises a balloon. A sheath is movably disposed over the balloon andthe actuator is coupled to the sheath to axially reposition the sheathrelative to the balloon. In this way the sheath may be used toselectively cover part of the balloon while exposing part of the balloonhaving a desired length, the sheath constraining the covered part fromexpansion.

In a further embodiment, the interventional element comprises a stentreleasably carried by the shaft. The actuator controls the length of adeployable portion of the stent, the deployable portion being releasedfrom the shaft while an undeployed portion of the stent remainsassociated with the shaft. In one embodiment, the actuator is coupled toa sheath which may be axially positioned to cover a first portion of thestent while a second portion of the stent having a desired length isleft uncovered for deployment. The stent may be either balloonexpandable or self-expanding. In a preferred embodiment, the stent iscomprised of a plurality of separable stent segments and stent length iscontrolled by exposing a desired number of stent segments outside of thesheath.

In one embodiment, the actuator is movable through a distance correlatedwith the length. For example, the actuator may be movable through astroke, each stroke of the actuator adjusting the length a predeterminedamount. The actuator may also be configured to allow the length to beadjusted in a first direction and prevent or limit the adjustment oflength in a second direction. For example, the actuator may comprise aratchet mechanism that allows the actuator to move in a first directionto increase the length of the interventional element, but prevents theactuator from moving in the reverse direction to decrease the length.

In some embodiments the indication device is coupled to the actuator.For example, the indication device may comprise a stop that limits themovement of the actuator, thus providing the user a tactile indicationof the length. Alternatively, the indication device may comprise asensor that senses movement of the actuator. Further, the indicationdevice may comprise a visual indicator coupled to the actuator (or to asensor associated with the actuator) to provide a visual indication ofthe length of the interventional element based on the actuator position.

The indication device may alternatively comprise a sensor that detectsthe length of the interventional element. In one embodiment, the sensormay be disposed near the distal end of the shaft and is coupled to anindicator at the proximal end, the indicator being a display or otheroutput device. The sensor may be mechanical, optical, magnetic,inductive, or other suitable type for detecting the length of theinterventional element. The output device may provide a visual, audible,tactile, or other signal to the user.

In a further aspect, the indication device comprises a plurality ofholes and a movable detent associated with the shaft, each hole beingconfigured to receive the detent, whereby adjusting the length moves thedetent from one hole to another hole. As the detent moves from one holeto the next, the reception of the detent in one of the holes provides atactile indication of the length of the interventional element. Inembodiments where a sheath is movably disposed over the shaft to adjustthe length of a balloon, stent or other interventional element, thedetent or the holes may be disposed on the sheath such that axialmovement of the sheath moves the detent from hole to hole.

In a further aspect, the invention provides a stent delivery cathetercomprising an elongated flexible shaft having distal and proximal endsand a stent releasably mounted at the distal end, a deployable portionof the stent being releasable from the catheter to assume an expandedconfiguration, the deployable portion having a length. An actuator isdisposed near the proximal end for controlling the length of thedeployable portion, and an indication device is disposed on the catheterfor indicating the length of the deployable portion to the user.

In some embodiments the actuator is movable through a distancecorrelated with the length of the portion of the stent to be deployed.For example, the actuator may be movable through a stroke correspondingto a preselected length. This allows the actuator to be actuatedrepeatedly to adjust the length of the stent to a desired multiple ofthe preselected length. In exemplary embodiments the stent comprises aplurality of stent segments, and the stroke corresponds to a segmentlength of one of the stent segments.

The invention contemplates various types of indication devicesassociated with the catheter. In one embodiment, the indication devicecomprises a stop that limits the movement of the actuator, thusproviding a tactile indication of the length. The actuator or ratchetmechanism may also be configured to emit an audible sound such as aclick that indicates the number of strokes or the distance through whichthe actuator has moved. The indication device may also comprise aplurality of holes or slots and a movable detent, each hole or slotbeing configured to receive the detent in a manner that can be felt bythe user. The indication device may also comprise a sensor for detectingthe length of the interventional element. The sensor may be disposed invarious locations along the shaft of the interventional device and isusually coupled to an indicator at the proximal end. The sensor may bemechanical, optical, magnetic, inductive, or other suitable type. Adisplay or other output means may be associated with the sensor forproviding a visual, audible, tactile, or other indication of the length.The indication device may be configured to indicate a length of thedeployable portion of the stent, the number of stent segments in thedeployable portion, the number of stent segments (or length of stent)remaining undeployed in the catheter, and other information.

In embodiments in which the stent comprises a plurality of separablestent segments, the actuator may be adapted to axially separate a firststent segment from a second stent segment prior to expansion thereof.This allows the second segment to be expanded and deployed withoutdeploying or interfering with the first segment. In an exemplaryembodiment, the actuator has a first position in which it is movable forcontrolling the number of stent segments in the deployable portion, anda second position in which it is movable for controlling the separationbetween the first and second stent segments.

The invention further provides methods of using an interventionalcatheter at a target site in a patient's body. In a first aspect, themethod comprises positioning an interventional element of theinterventional catheter near the target site with a proximal portion ofthe interventional catheter being disposed outside the patient's body. Aworking length of the interventional element is then adjusted with theinterventional element remaining positioned in the patient's body. Anindication of the working length of the interventional element isreceived from the proximal portion of the interventional catheter; and,after receiving the indication, the interventional element is deployed.

In exemplary embodiments, the interventional element comprises aballoon, and adjusting the working length comprises constraining a firstportion of the balloon from expansion while leaving a second portion ofthe balloon unconstrained from expansion. Preferably, constraining afirst portion of the balloon comprises covering the first portion of theballoon by a sheath movably disposed on the interventional catheter. Theindication of the working length then comprises an indication of thelength of the second portion.

In some embodiments, the sheath is coupled to an indicator, and theindication of working length being received from the indicator, whereinmoving the sheath changes the indication received from the indicator.Receiving the indication of working length may comprise observing avisual indication, hearing an audible indication, feeling a tangibleindication, or otherwise receiving a signal from the catheter indicativeof the working length. A visual indication may comprise one or moreindicia displayed electronically, mechanically, or otherwise on theproximal portion of the interventional catheter. A tactile indication ofworking length may be received from a detent engaging a hole or otherstructure associated with the interventional catheter. An audibleindication of working length may be received from a clicker or othernoise emitter associated with the actuator.

The method may further include, after deploying the interventionalelement, positioning the interventional element near a second targetsite; adjusting the working length of the interventional element to asecond working length; receiving from the interventional catheter asecond indication of the second working length; and after receiving thesecond indication, re-deploying the interventional element.

In a further aspect of the invention, a method of deploying a stent at atarget site in a patient's body comprises positioning a distal end of adelivery catheter near the target site, the stent being releasablycoupled to the distal end, a proximal portion of the delivery catheterbeing disposed outside the patient's body; adjusting the length of adeployable portion of the stent with the delivery catheter positioned inthe patient's body; receiving an indication of the length from theproximal portion of the delivery catheter; and after receiving theindication, deploying the deployable portion of the stent at the targetsite. The indication of working length may be received visually,audibly, tactilely, or in another humanly detectable manner.

Adjusting the length of the deployable portion may comprise moving anactuator associated with the proximal portion of the delivery catheterthrough a distance correlated with the length. For example the actuatormay be movable through a stroke, each stroke of the actuator adjustingthe length a predetermined amount. The stent may comprise a plurality ofstent segments, and the stroke may then correspond to a segment lengthof one of the stent segments. The indication device may comprise a stopthat limits the movement of the actuator, thus providing tactileindication of length.

The indication of the length may be received from an output deviceassociated with the proximal end of the catheter. The output device maybe coupled to a sensor, and the method further comprises detecting thelength with the sensor. The sensor may be disposed in any suitablelocation in the catheter, but in an exemplary embodiment is disposednear the distal end of the delivery catheter in proximity to the stent.The sensor may detect the length mechanically, optically, magnetically,inductively, or in other ways. In other embodiments, the tactileindication is received from a detent engaging a hole associated with thedelivery catheter.

In some embodiments, the stent comprises separable stent segments, andadjusting the length comprises constraining at least a first stentsegment from expansion while leaving at least a second stent segmentunconstrained from expansion. Adjusting the length may comprise moving asheath relative to the stent segments for selectively covering the firststent segment and exposing the second stent segment. In suchembodiments, the indication of length may be correlated with the numberof stent segments. Alternatively, the indication of length may becorrelated with movement of the sheath relative to the stent.

The method of the invention may further include axially separating thefirst stent segment from the second stent segment prior to expansionthereof. Such separation may be accomplished using an actuatorassociated with the proximal portion of the delivery catheter. Theactuator may be movable to a first position for controlling the numberof stent segments in the deployable portion and further movable to asecond position for controlling the separation between the first andsecond stent segments.

Further aspects of the nature and advantages of the invention will beappreciated from the following detailed description taken in conjunctionwith the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side partial cutaway view of a stent delivery catheteraccording to the invention with the sheath retracted and expandablemember in an expanded configuration.

FIGS. 2A-2B are side views of the stent delivery catheter of FIG. 1 withthe distal portion in cross-section showing the expandable member inunexpanded and expanded configurations, respectively.

FIG. 3 is a side cross-sectional view of a portion of the shaft of thestent delivery catheter of the invention in a further embodimentthereof.

FIG. 4A is a side cross section of a distal portion of the post in thehandle of the stent delivery catheter of the invention in anotherembodiment thereof.

FIG. 4B is a transverse cross section of the post of FIG. 4A.

FIG. 5A is a side cross section of the post of the handle of the stentdelivery catheter of the invention in a further embodiment thereof.

FIG. 5B is a transverse cross section of the post of FIG. 5A.

FIG. 5C is a top elevational view of a clip within the post of FIG. 5A.

FIG. 6A is a side cutaway view of the handle of the stent deliverycatheter of FIG. 1 with the lever in a down position.

FIG. 6B is a bottom cutaway view of the handle of FIG. 6A.

FIG. 7A is a side cutaway view of the handle of the stent deliverycatheter of FIG. 1 with the lever in an up position.

FIG. 7B is a bottom cutaway view of the handle of FIG. 7A.

FIGS. 8A-8B are side elevational views of the handle of the stentdelivery catheter of FIG. 1 showing the sheath in unretracted andretracted positions, respectively.

FIG. 8C is a side elevational view of a further embodiment of a handlein the stent delivery catheter of the invention.

FIGS. 9A-9B are side elevational views of a further embodiment of thehandle of the stent delivery catheter of the invention showing the leverin down and up positions, respectively.

FIGS. 10A-10B and 10C-10D are oblique and transverse cross-sectionalviews, respectively, of the interior of the handle of FIGS. 9A-9B.

FIGS. 11A-11B are oblique views of the interior of a further embodimentof a handle in the stent delivery catheter of the invention.

FIGS. 12A-12B, 13, and 14 are side cross-sectional views of a distalportion of a stent delivery catheter according to the invention in afurther embodiment thereof showing alternative sensory devices.

FIG. 15A is a side cutaway view of the handle of the stent deliverycatheter of the invention in yet another embodiment thereof.

FIG. 15B is a side elevational view of the handle of FIG. 15A.

FIG. 15C is a bottom cutaway view of the handle of FIG. 15A.

FIG. 16 is an oblique view of the internal components of the handle ofthe stent delivery catheter of the invention in still another embodimentthereof.

FIG. 17 is a cutaway view of the interior of the handle of a stentdelivery catheter according to the invention in a further embodimentthereof.

FIG. 18A is a cutaway view of the handle of a stent delivery catheteraccording to the invention in yet another embodiment thereof.

FIG. 18B is a close-up view of a portion of the handle of FIG. 18A.

FIG. 18C is an oblique view of the actuator knob of the handle of FIG.18A.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

The invention provides devices and methods for manipulation ofinterventional catheters with greater control, precision, andvisibility. In one aspect, the devices and methods of the inventionfacilitate controlling the working length of an interventional elementon a catheter and indicating the working length to the user. In anexemplary embodiment, the interventional element is an expandable membersuch as a balloon for dilatation of vascular lesions. The interventionalelement also may comprise a stent or series of stent segments. However,the principles of the invention will have applicability to various typesof interventional elements for use in various parts of the body,wherever highly precise catheter manipulation and control and visibilityof working length may be desirable.

Referring to FIG. 1, in a first embodiment of the invention, a stentdelivery catheter 20 comprises an elongate flexible shaft 22 having aproximal end 24 and a distal end 26. Shaft 22 is comprised of aplurality of coaxial members including an inflation shaft 34, a pusher36, and a sheath 38. A handle 28 is mounted to sheath 38 at proximal end24. Near distal end 26, expandable member 30, shown in an expandedconfiguration, is mounted at its proximal end to inflation shaft 34. Aguidewire tube 40 extends through a port 42 in sheath 38 and extendsthrough the interior of expandable member 30 to distal end 26.Expandable member 30 is attached at its distal end to guidewire tube 40,and a nosecone 32 is mounted to guidewire tube 40 distally of expandablemember 30. A guidewire 44 is slidably positionable through guidewiretube 40 and nosecone 32 to facilitate guidance of catheter 20 throughthe vasculature.

A plurality of stent segments 46 are slidably positioned over expandablemember 30. Pusher 36 is axially slidable relative to inflation shaft 34and engages stent segments 46 at its distal end 48. Pusher 36 may bepushed distally to advance stent segments 46 over expandable member 30,or pusher 36 may be held in a stationary position while expandablemember 30 is drawn proximally relative to stent segments 46. Sheath 38is axially movable relative to expandable member 30, pusher 36, andstent segments 46. Sheath 38 may be repositioned proximally or distallyto selectively expose a desired length of the expandable member andstent segments thereon according to the length of the lesion to betreated. Sheath 38 and pusher 36 may be drawn proximally in tandemrelative to expandable member 30 to separate stent segments 46 exposeddistally of sheath 38 from stent segments 46 held within sheath 38.Various other aspects of the construction of delivery catheter 20 andstent segments 46 are described in copending application Ser. No.10/637,713, filed Aug. 8, 2003 (Attorney Docket No. 21629-000340), whichhas been incorporated herein by reference.

A stent valve 50 is mounted to the interior of sheath 38 and ispreferably spaced proximally from the distal end 52 of sheath 38 adistance equal to the length of about ½-1 stent segment. Stent valve 50comprises an annular ridge configured to frictionally engage stentsegments 46 to facilitate control of the spacing between those segmentsto be deployed distally of sheath 38 and those to be retained withinsheath 38. Stent valve 50 may also comprise any of the structuresdescribed in copending application Ser. No. 10/412,714, filed Apr. 10,2003, Attorney Docket No. 21629-000330, which is incorporated herein byreference.

Handle 28 includes an actuator knob 54 rotatably coupled thereto. A post56 is mounted to handle 28 so as to be extendable distally out of thehandle and retractable proximally into the handle. Sheath 39 is attachedto post 56. Rotation of actuator knob 54 extends or retracts post 56,thereby moving sheath 38 relative to expandable member 30. A lever 58 ispivotably coupled to handle 28 and is movable between a first positionin which rotation of actuator knob 54 moves only sheath 38, and a secondposition in which rotation of actuator knob 54 moves both sheath 38 andpusher 36 relative to expandable member 30, as described more fullybelow.

A plurality of indicia 60 are disposed on post 56. Indicia 60 comprisealphanumeric symbols or other appropriate indicators of the length ofexpandable member exposed distally of sheath 38 and/or the number orlength of stent segments 46 exposed for deployment. As described morefully below, a pointer or other reference object may be used that pointsto the appropriate location among indicia 60 corresponding to the numberor length of stent segments 46 that have been exposed; preferably suchpointer is adapted to compensate for retraction of sheath 38 in tandemwith pusher 36, during which additional stent segments are not exposeddistally of sheath 38, as described more fully below.

A luer fitting 62 is mounted to a proximal end of handle 28 and is influid communication with an inflation lumen (not shown in FIG. 1) ininflation shaft 34. Luer fitting 62 is adapted for coupling to aninflation device to enable delivery of inflation fluid into expandablemember 30, for example, an Indeflator™ inflation device available fromGuidant Corp. of Santa Clara, Calif.

Referring to FIGS. 2A-2B, delivery catheter 20 includes a device forproviding a tactile indication of the number of stent segments 46exposed from sheath 38 in addition to the visual indication provided byindicia 60. In this embodiment, the indication device consists of adetent 66 extending inwardly from the inner wall of sheath 38, and aseries of slots 68 arranged axially at spaced-apart locations on pusher36. Detent 66 and slots 68 may be located in a distal portion ofdelivery catheter 20 just proximal to expandable member 30, in a middleportion of the catheter proximal to guidewire port 42, or near theproximal end 24 distally of or within post 56 or handle 28. Detent 66 ispreferably a cantilevered extension integrally formed with sheath 38,being cut, for example, out of the wall of sheath 38, and is resilientlydeflectable and biased toward pusher 36. Detent 66 may alternatively bea bump or ridge on the inner wall of sheath 38 configured to engageslots 68. Slots 68 may be holes, apertures, depressions, recesses,ridges, bumps or any other suitable structure for receiving or catchingon detent 66. The spacing of slots 68 is selected to provide anindication of the distance that sheath 38 is translated relative topusher 36. In a preferred embodiment, the spacing is equal to the lengthof 1 stent segment 46, although ½, twice, or other known fraction ormultiple of the length of a stent segment 46 are also possible. Assheath 38 is retracted proximally relative to pusher 36, detent 66catches in each slot, providing a tactile “bump” that can be feltthrough handle 28. In this way, as knob 54 is turned to retract sheath38, the user knows that each bump corresponds to the length of one stentsegment, meaning that one stent segment has been exposed distally ofsheath 38 with each bump. By feeling such bumps and by observing indicia60, the user can precisely retract the sheath to expose the number ofstent segments needed to match the length of the lesion being treated,as illustrated in FIG. 2B.

In a further embodiment, illustrated in FIG. 3, delivery catheter 20further includes a device for providing a tactile indication of thedistance that both sheath 38 and pusher 36 are retracted in tandemrelative to expandable member 30. In this embodiment, a second detent 70is disposed on the outer wall of inflation shaft 34 and extendsoutwardly to engage a series of axially spaced slots 72 in pusher 36.Detent 70 and slots 72 may be constructed similarly to detent 66 andslots 68 described above, and may be located in a distal, middle, orproximal portion of delivery catheter 20. The spacing of slots 72 isselected to provide the user with an indication of the distance thatpusher 36 is retracted relative to the expandable member 30. Forexample, after sheath 38 has been retracted relative to pusher 36 andexpandable member 30 so as to expose a desired number of stent segments,the user may wish to create separation between the stent segments 46exposed distally of sheath 38 and those stent segments 46 remainingwithin sheath 38. This is accomplished by retracting both sheath 38 andpusher 36 in tandem, wherein detent 66 is stationary relative to slots68. As sheath 38 and pusher 36 are retracted, detent 70 moves from oneslot 72 to another, providing a tactile “bump” that can be felt throughhandle 28. The currently preferred separation distance is about ½-1times the length of one stent segment 46. Thus, with slots 72 spacedapart a distance of ½ stent segment, after exposing the desired numberof stent segments, the user can retract pusher 36 and sheath 38 one ortwo “bumps” to create the desired separation.

FIGS. 4A-4B and 5A-5C illustrate alternative embodiments of a detent forproviding a tactile indication of the degree of sheath retraction to theuser. In FIGS. 4A-4B, a detent 74 is located within a block 76 at thedistal end of post 56 on handle 28. An axial passage 78 extends throughpost 56 and block 76. At the distal end of axial passage 78, sheath 38is fixed to block 76 by adhesive, set screw, or other suitable means ofattachment. Pusher 36 extends slidably through passage 78. A bullet 80is fixed within passage 78 and has an interior lumen 82 of sufficientsize that pusher 36 is slidable therein. A detent pin 84 is disposedtransversely through bullet 80 and cuts through lumen 82 along an upperedge thereof, as seen in FIG. 4B. Pusher 36 has a series of transverseslots 86 in axially-spaced locations aligned with detent pin 84. In thisway, as sheath 38 is retracted relative to pusher 36, detent pin 84engages and seats in each slot 86, allowing the user to feel a bump aseach slot is engaged.

In the embodiment of FIGS. 5A-5C, detent 74 is again located withinblock 76 at the distal end of post 56. In this embodiment, however,detent 74 comprises a C-shaped clip 88 disposed within an annularchannel 89 in bullet 80. C-shaped clip 88 is a fairly hard, resilientmaterial such as nickel titanium alloy or other suitable metal orpolymer. C-shaped clip 88 is positioned so as to cut through lumen 82along an upper edge thereof in alignment with slots 86 on pusher 36.Again, as sheath 38 is retracted relative to pusher 36 C-shaped clip 88engages and seats within each slot 86, providing tactile feedback to theuser as to the degree of sheath retraction and number of stent segments46 exposed distally thereof for deployment.

FIGS. 6A-B and 7A-B illustrate the interior of handle 28 with lever 58in “down” and “up” positions, respectively. Handle 28 has a housing 90having an ergonomic shape designed for gripping in one hand. Actuatorknob 54 is rotatably coupled to housing 90 in a location suitable forengagement with the user's thumb or forefinger. Post 56 extends slidablythrough the distal end of housing 90 and has a rack 92 disposed on anupper surface thereof. A pinion gear 96 is mounted to actuator knob 54for rotation therewith. Pinion gear 96 engages rack 92 such thatrotation of actuator knob 54 translates post 56, along with sheath 38mounted thereto, distally or proximally relative to handle 28.

Pusher 36 extends slidably through post 56 as described above and isfixed at its proximal end to a puck 98. Puck 98 is pivotably coupled toa brake 100, which is slidably mounted to a rail 102. Rail 102 iscoupled to lever 58 at its proximal end and to a hinge 104 at its distalend such that movement of lever 58 from the down position of FIGS. 6A-Bto the up position of FIGS. 7A-B rotates rail 102 along with brake 100about an axis A. Springs 106 at each end of rail 102 bias lever 58toward the up and down positions.

Brake 100 has a plurality of teeth 108, 110 along opposing lateral edgesthereof, as seen in FIG. 6B. A brake rack 112 is mounted to the innersurface of housing 90 and has a series of teeth configured to engageteeth 108 of brake 100. When lever 58 is in the down position of FIGS.6A-B, teeth 108 engage brake rack 112, thus holding pusher 36 in astationary position relative to handle 28. In this way, as knob 54 isrotated, sheath 38 is retracted relative to both pusher 36 and inflationshaft 34 to expose stent segments 46 on expandable member 30 distally ofsheath 38.

Referring to FIGS. 7A-B, a coupling rack 114 is disposed on a lowersurface of post 48 and has a plurality of teeth configured to engageteeth 110 on brake 100. With lever 58 in the up position, teeth 108 onbrake 100 are disengaged from brake rack 112 and teeth 110 (not visiblein FIGS. 7A-B) are engaged with coupling rack 114. This allows pusher 36to move in tandem with post 56 and sheath 38. In this manner, rotationof actuator knob 54 retracts both sheath 38 and pusher 36 relative toinflation shaft 34, allowing separation to be created between stentsegments 46 exposed distally of sheath 38 and those stent segments 38retained within sheath 38.

Referring now to FIGS. 8A-8B, visual indication devices for indicatingthe extent of sheath retraction or the number of stent segments exposedfrom sheath 38 will be described. In a preferred embodiment, post 56 hasan axial slot or window 118 disposed lengthwise thereon. Indicia 60 areapplied to post 56 adjacent to window 118 or on a translucent cover overwindow 118. An indicator 120 of contrasting color is mounted to pusher36 within post 56 in alignment with window 118. In this way, as post 56is retracted relative to pusher 36, indicia 60 move relative toindicator 120. In a preferred embodiment, indicia 60 comprise numberscorresponding to the number of stent segments 46 carried by deliverycatheter 20. The indicator 120 may be configured to point to the numberof stent segments 46 exposed for deployment as sheath 38 is retracted.Alternatively, indicator 120 may be configured to point to the number ofstent segments 46 remaining within sheath 38. It should further be notedthat when lever 58 is moved to the up position of FIG. 8B, whereinsheath 38 and pusher 36 move in tandem, indicator 120 remains stationaryrelative to indicia 60 so that the process of creating separationbetween stent segments 46 does not alter the indication of the number ofstent segments being deployed.

FIG. 8C illustrates another embodiment of visual indicators on post 56.As in the embodiment of FIGS. 8A-B, an axial slot 119 is disposed inpost 56 to expose an indicator bar 121, which is fixed to pusher 36 andis movable relative to post 56. A first series of indicia 123 aredisposed on post 56 adjacent slot 119. As stent segments 46 are exposedand deployed, indicator bar 121 moves relative to first indicia 123 toindicate the number of stent segments 46 remaining within sheath 38. Asecond set of indicia 125 are disposed on post 56 on the opposite sideof slot 119 from first indicia 123 and move with post 56 relative to areference point fixed relative to handle 28. In an exemplary embodiment,the reference point is the distal edge 127 of handle 28. As sheath 38 isretracted, second indicia 125 indicate the length or number of stentsegments 46 being exposed distally of sheath 38.

In an alternative embodiment, illustrated in FIGS. 9A-B, a window 122 isdisposed in handle 28, with indicia 60 applied adjacent to window 122 orto a translucent cover thereon. An indicator 124 is mounted to post 56within handle 28 and is visible through window 122 when lever 58 is inthe down position of FIG. 9A. Retraction of post 56 thus moves indicator124 relative to indicia 60. Following sheath retraction, when separationis to be created between stent segments 46, lever 58 is moved to an upposition as in FIG. 9B and indicator 124 is no longer visible throughwindow 122. As shown in FIGS. 10A-10D, indicator 124 is mounted to anangled arm 126 pivotably coupled to an axle 128 aligned with the axis ofrotation of lever 58. As lever 58 is pivoted to its up position as inFIGS. 10B and 10D, rail 102 engages arm 126 and pivots indicator 124laterally, thereby displacing it from window 122. When lever 58 isreturned to the down position as in FIGS. 10A and 10C, rail 102 againengages arm 126 and returns indicator 124 to a position in which it isvisible through window 122.

In a further embodiment, stent delivery catheter 20 includes a ratchetmechanism serving to provide an audible and/or tangible indication ofsheath retraction, as well as to limit travel of the sheath to a singledirection (e.g. proximal). Preferably the ratchet may be selectivelyenabled, so that the ratchet is engaged when sheath 38 is retractedrelative to pusher 36, but is disengaged when sheath 38 and pusher 36are retracted together relative to expandable member 30. In an exemplaryembodiment, illustrated in FIGS. 11A-11B, a ratchet frame 130 is mountedto hinge 104, which, as described above with reference to FIG. 6-7, iscoupled to rail 102 and pivots therewith when lever 58 is actuated.Ratchet frame 130 has a pawl 132 configured to engage a rack 134 on post56. Rack 134 has a series of stepped teeth 136 oriented so as to beslidable proximally relative to pawl 132, but in the distal directionpawl 132 engages the vertical trailing edges of teeth 136 to stop distalmovement. Pawl 132 is flexible and resilient so as to ride up over eachtooth and spring back at the vertical trailing edge, making an audibleand tangible “click.” When lever 58 is in the down position of FIGS.6A-6B so as to lock pusher 36 relative to handle 28, hinge 104 isdisposed in the position shown in FIG. 11A, urging pawl 132 intoengagement with rack 134. This limits sheath movement to the proximaldirection and causes pawl 132 to create an audible and tangibleindication of sheath retraction. When lever 58 is flipped to the “up”position of FIGS. 7A-7B wherein pusher 36 becomes fixed relative tosheath 38, ratchet frame 130 pivots with hinge 104 away from post 56,disengaging pawl 132 from rack 134, as shown in FIG. 11B. This allowsthe user to adjust the separation distance of exposed stents segmentsrelative to unexposed stent segments without restriction on the movementof sheath 38 and pusher 36. It will be understood that the ratchetmechanism described above is only exemplary and mechanisms of varioustypes and at various locations in stent delivery catheter 20 arepossible. For example, a circular rack of stepped teeth could be coupledto knob 54, and a pawl could be mounted within handle 28 so as to engagethe rack as knob 54 is rotated, as described more fully below.

The interventional catheters of the invention may further includesensory devices for detecting the relative positions of cathetercomponents, the length of balloon or stent exposed for deployment, thenumber of stent segments exposed, and other parameters. In a firstembodiment illustrated in FIG. 12A, a sensor 140 is mounted to the innerwall of sheath 138 and is adapted to detect its position relative toinflation shaft 34 and/or pusher 36. Sensor 140 may be any of varioustypes, but in one embodiment comprises an optical encoder capable ofdetecting a series of marks or lines 142 disposed on the outer surfaceof inflation shaft 34 (alternatively such marks could be placed on theoutside of pusher 36). Sensor 140 includes a wire 144 extendingproximally through sheath 38 into handle 28, where it may be coupled toan appropriate power supply and output device for displaying thedetected position. Alternatively sensor 140 may be wireless and maytransmit signals via radio waves, infrared signals, or other suitablemanner. Various types of suitable optical encoders are available,including those described in U.S. Pat. No. 5,965,879, which isincorporated herein by reference. Alternatively, sensor 140 could be amagnetic or inductive sensor and a series of ferromagnetic stripes orbands could be applied to pusher 36 in place of marks 142.

It should be noted that sensor 140 may be placed in virtually anylocation along the extremity of delivery catheter 20 from handle 28 toexpandable member 30. Preferably, however, sensor 140 is located nearthe distal end of delivery catheter 20. This has the advantage ofproviding a precise indication of the actual displacement of sheath 38near the distal end, without distortion as a result of the stretching orcompression of sheath 38, pusher 36, or inflation shaft 34. In anotherconfiguration, illustrated in FIG. 12B, sensor 140 is mounted near thedistal end 52 of sheath 38. Sensor 140 is adapted for detecting eachstent segment 46 or each strut within stent segments 46 as sheath 38 isretracted past each segment. For example, sensor 140 may be an opticalencoder capable of detecting and counting the struts of each stentsegment or suitable markings on each stent segment. As anotheralternative, a series of opaque or reflective marks may be applied toexpandable member 30, stent segments 46, or guidewire tube 40 that canbe optically detected by sensor 140 as sheath 38 is retracted.

In a further embodiment, illustrated in FIG. 13, a sensor 146 is mountedto the inner wall of sheath 38 near its distal end 52. Sensor 146 may beany of a variety of types suitable for sensing the displacement ofsheath 38 relative to stent segments 46, expandable member 30, orguidewire tube 40. For example, sensor 146 may be a magnetic sensor, anda plurality of magnetic bands 148 may be mounted to guidewire tube 40within expandable member 30. As sheath 38 is retracted relative toguidewire tube 40, sensor 146 detects each magnetic band 148, which maybe spaced apart a known distance such as the length of one stent segment46. A wire 150 extends from sensor 146 proximally through sheath 38 tohandle 28, where it is coupled to a suitable power supply, processor,and output display (or sensor 146 could be wireless). The output display(or audible output device) may display the number of stent segments, thelength of stent segments, or the length of expandable member 30 that hasbeen exposed distally of sheath 38.

In another embodiment, illustrated in FIG. 14, a displacement sensor 150is mounted to sheath 38 just proximal to port 42 through which guidewiretube 40 extends. Displacement sensor 150 may be a draw-wire displacementsensor (or so-called “electronic tape measure”) that has an extendablewire 152 biased to retract into a housing 154 (see for example,www.micro-epsilon.com). Wire 152 extends through a hole 153 in guidewiretube 40 and passes slidably through guidewire tube 40 into nosecone 32.Wire 152 has an anchor 155 at its distal end that is fixed to nosecone32. As sheath 38 is retracted, wire 152 is extended from housing 154. Anencoder within housing 154 (not shown) detects the length of wire thathas been drawn out (or the number of rotations of a spool around whichthe wire is wound). A conductor wire 156 extends proximally into handle28 and is coupled to an appropriate power supply, processor, and outputdisplay. The exact displacement of sheath 38 relative to nosecone 32(and expandable member 30) is thus detected and indicated to the user.Of course, displacment sensor 150 may be mounted at any suitablelocation along stent delivery catheter 20, including within handle 28,and may be adapted to detect the displacement of any of the variousmovable components including sheath 38, pusher 36, inflation shaft 34,or stent segments 46.

FIGS. 15A-15C illustrate still another embodiment of a stent deliverycatheter according to the invention. In this embodiment, handle 28 isconstructed in the manner described above except in place of actuatorknob 54, a motor 160 is mounted to housing 90. Motor 160 may be astepper, servo, or other suitable motor of appropriate size anddelivering the necessary level of torque, speed, and power. A driveshaft 162 of motor 160 is coupled to pinion gear 96. Motor 160 iscoupled to a switch 164 and a power supply such as a battery (notshown). In addition, motor 160 includes an encoder (not shown) thatdetects the degree of rotation of drive shaft 162. The encoder may becoupled to a processor 166 and an output display 168 that is visiblethrough handle housing 90. In this way, motor 160 may be actuated usingswitch 164 to rotate pinion gear 96 and thereby retract post 56 andsheath 38. The user can view the amount of retraction (by either numberof stent segments or their length) on display 168. Preferably switch 164may be actuated in two directions so as to move motor 160 either forwardor backward, thus allowing precise control of the position of sheath 38.

In a preferred embodiment, switch 164 is adapted to enable the user toselect the desired amount of sheath retraction, whereupon motor 160 willautomatically retract sheath 38 the appropriate amount. For example,switch 164 could be pressed once to retract the sheath the length of onestent segment, twice for two stent segments, etc. Alternatively, a dialor sliding switch could be used so that various switch positions or thedegree of switch displacement corresponded to the desired amount ofretraction. In these embodiments, motor 160 could include a feedbackloop from its encoder so that motor 160 automatically rotated driveshaft 162 the amount needed to achieve the desired degree of sheathretraction.

FIG. 16 illustrates a further embodiment of a stent or balloon lengthindication device according to the invention. The figure illustrates theinternal components of handle 28 with handle housing 90 removed,including post 56 to which sheath 38 (not shown) is fixed, brake 100 towhich pusher 36 (not shown) is fixed, ratchet frame 130 and pawl 132that engages rack 134, and actuator knob 54 that drives post 56 distallyand proximally. In this embodiment, brake 100 is pivotably coupled to adetent block 170 by an axle 172 extending between ratchet frame 130 andlever 58. Detent block 170 and brake 100 are slidable along axle 172relative to post 56 to enable positioning of pusher 36 relative tosheath 38. A series of detent slots 174 are disposed in an axial linealong the lateral side of post 56 proximal to rack 134. A threaded hole176 extends through detent block 170 and is configured to receive adetent ball (not shown) sized to engage detent slots 174. A spring (notshown) is inserted in hole 176 behind the detent ball to urge it towarddetent slots 174, and a threaded set screw (not shown) is then threadedinto hole 176 to hold the spring and detent ball in place. As detentblock 170 moves axially relative to post 56, the detent ball engageseach detent slot 174 producing an audible click and/or tangible bumpdetectable by the user. The spacing between each detent slot 174 isselected to be a known distance, e.g., the length of one stent segment46 or a multiple or fraction thereof. In this way, as the user retractssheath 38 relative to pusher 36 (and expandable member 30), the userreceives an audible or tangible indication of the length of balloon, thelength of stent, or the number of stent segments exposed for deployment.

It will be understood that detents and similar features to providetactile feedback to the user as the length of the interventional element(stent, balloon, etc.) is adjusted may be positioned in various placesin the handle or shafts of the interventional catheters of theinvention. In still another embodiment, not illustrated, a series ofdetent holes may be positioned in a circular pattern on the underside ofknob 54, and a spring-loaded ball plunger may be mounted to handle 28 inalignment with the detent holes so as to be received therein as knob 54is rotated. In this way, the user will feel a “bump” or “click” eachtime the ball plunger engages one of the detent holes. Again, thespacing of the detent holes may be selected to correspond with a knowndistance such as the length of one of stent segments 46 to provide anindication of the length of the interventional element as it is exposedfor deployment.

FIG. 17 illustrates a further embodiment of the invention employing anactuator 180 having a limited stroke such that each actuation exposes apreselected length of a balloon, stent or other interventional element.Actuator 180 comprises a trigger 182 pivotably coupled to handle housing90. A ratchet wheel 184 is fixed to trigger 182 so as to rotatetherewith, and has a plurality of pawls 186 extending outwardlytherefrom. Pawls 186 are resiliently deflectable radially inwardly. Aspring 190 extending between trigger 182 and block 192 on handle housing90 biases trigger 182 distally. A stop 194 on handle housing 90 limitsthe proximal motion of trigger 182. A lower gear 196 is concentricallymounted over ratchet wheel 184 and has inner one-way teeth 198 and outerteeth 200. An upper gear 201 is rotatably mounted to handle housing 90and has teeth 202 engaged by outer teeth 200. Teeth 202 mate with rack92 on post 56 (which is coupled to sheath 38, not shown).

In operation, trigger 182 is pulled proximally by the user, therebyrotating ratchet wheel 184. Pawls 188 engage inner one-way teeth 198,turning lower gear 196 in a counter-clockwise direction. Outer teeth 200engage teeth 202, turning upper gear 201 in a clockwise direction,thereby moving post 56 in a proximal direction relative to handlehousing 90. This retracts sheath 38 relative to inflation shaft 34,exposing stent segments 46. The location of stop 194 can be selected sothat each stroke of trigger 182 exposes a desired length of balloon orstent. For example, each trigger stroke may correspond to the length ofone stent segment 46, allowing the user to actuate the trigger once foreach stent segment s/he wishes to deploy. When trigger 182 is released,spring 190 pulls it back in the distal direction and pawls 188 aredeflected and slide over inner one-way teeth 198 so that post 56 andsheath 38 remain in the retracted position.

A further embodiment of a ratchet mechanism for one-way deployment of aninterventional element according to the invention is illustrated inFIGS. 18A-18C. In this embodiment, a pawl 206 is mounted to handlehousing 90 and has a tooth 208 that engages a rack 210 on the undersideof knob 54. Pawl 206 has a flat base 212 mounted to handle housing 90and a resilient inclined extension 214 to which tooth 208 is mounted.Rack 210 has one-way teeth 211 that allow tooth 208 to slide over themas knob 54 is rotated in a first direction, but that engage tooth 208and prevent rotation in the opposite direction. A camming bar 216 ismounted over pawl 206 and is axially slidable relative thereto. A thumbpad 218 is mounted to the proximal end of camming bar 216. By exertingdistal pressure on thumb pad 218, camming bar 216 slides distally,engaging inclined extension 214 and pushing it downward relative to knob54. This disengages tooth 208 from rack 210. By retracting camming bar216, inclined extension 214 recoils toward knob 54 so that tooth 208again engages rack 210.

It will be understood that various types of mechanisms may be used toprovide one-way actuation in the interventional catheter of theinvention. In another exemplary embodiment, not illustrated, aunidirectional roller clutch may be used to couple knob 54 to piniongear 96 (or to a shaft fixed thereto). Such a roller clutch transmitstorque in a first direction while overrunning freely in the oppositedirection. In this way, when rotated in a first direction knob 54 turnspinion gear 96 thereby retracting sheath 38, but when rotated in theopposite direction knob 54 turns freely without turning pinion gear 96.Suitable unidirectional roller clutches are available from, e.g., StockDrive Products, www.sdp-si.com.

While the above is a complete description of the preferred embodimentsof the invention, it will be appreciated that various alternatives,modifications, additions and substitutions are possible withoutdeparting from the scope of the invention, which is defined by theclaims.

1. A catheter comprising: an elongated flexible shaft having a distalend and a proximal end; an interventional element at the distal end, theinterventional element having an adjustable length, an actuator at theproximal end for adjusting the length of the interventional element; andan indication device at the proximal end for indicating the length. 2.The catheter of claim 1 wherein the interventional element comprises aballoon.
 3. The catheter of claim 2 further comprising a sheath slidablydisposed over the balloon, actuator being coupled to the sheath toaxially reposition the sheath relative to the balloon.
 4. The catheterof claim 1 wherein the interventional element comprises a stentreleasably coupled to the shaft.
 5. The catheter of claim 4 wherein theactuator controls the length of a deployable portion of the stent, thedeployable portion being released from the shaft while an undeployedportion of the stent remains coupled to the shaft.
 6. The catheter ofclaim 1 wherein the actuator is movable through a distance correlatedwith the length.
 7. The catheter of claim 1 wherein the actuator ismovable through a stroke, each stroke of the actuator adjusting thelength a predetermined amount.
 8. The catheter of claim 1 wherein theindication device comprises a stop that limits the movement of theactuator.
 9. The catheter of claim 1 wherein the indication devicecomprises a sensor for detecting the length of the interventionalelement.
 10. The catheter of claim 9 wherein the sensor is disposed neara distal end of the shaft, the sensor being coupled to an indicator atthe proximal end.
 11. The catheter of claim 9 wherein the sensor isoptical.
 12. The catheter of claim 9 wherein the sensor is magnetic. 13.The catheter of claim 9 further comprising a display associated with thesensor for displaying an indication of the length.
 14. The catheter ofclaim 1 wherein the indication device provides a visual indication ofthe length.
 15. The catheter of claim 1 wherein the indication deviceemits an audible indication of the length.
 16. The catheter of claim 1wherein the indication device provides a tactile indication of thelength.
 17. The catheter of claim 1 wherein the indication devicecomprises a plurality of holes and a movable detent, each hole beingconfigured to receive the detent, whereby adjusting the length moves thedetent from one hole to another hole.
 18. The catheter of claim 17wherein the reception of the detent in one of the holes provides atactile indication of the length of the interventional element.
 19. Thecatheter of claim 1 wherein the actuator comprises a ratchet mechanismthat allows adjustment of the length in a first direction and preventsadjustment of the length in a second direction.
 20. A cathetercomprising: an elongated flexible shaft having a distal end a proximalend; an expandable member mounted at the distal end of the shaft, theexpandable member being expandable to an expanded configuration havingan expanded length; a sheath axially movable relative to the shaft andbeing positionable around at least a portion of the expandable member torestrain the expansion thereof; an actuator at the proximal end forcontrolling the position of the sheath relative to the expandable memberto adjust the expanded length; and an indication device on the catheterfor indicating the expanded length.
 21. The catheter of claim 20 furthercomprising at least one stent releasably positioned over the expandablemember.
 22. The catheter of claim 21 wherein the actuator controls thelength of a deployable portion of the stent, the deployable portionbeing released from the shaft while an undeployed portion of the stentremains coupled to the shaft.
 23. The catheter of claim 20 wherein theactuator is movable through a distance correlated with the expandablelength.
 24. The catheter of claim 20 wherein the actuator is movablethrough a stroke, each stroke of the actuator adjusting the expandablelength a predetermined amount.
 25. The catheter of claim 20 wherein theindication device comprises a stop that limits the movement of theactuator.
 26. The catheter of claim 20 wherein the indication devicecomprises a sensor for detecting the length of the interventionalelement.
 27. The catheter of claim 26 wherein the sensor is disposednear a distal end of the shaft, the sensor being coupled to an indicatorat the proximal end.
 28. The catheter of claim 26 wherein the sensor isoptical
 29. The catheter of claim 26 wherein the sensor is magnetic. 30.The catheter of claim 26 further comprising a display associated withthe sensor for displaying an indication of the length.
 31. The catheterof claim 20 wherein the indication device provides a visual indicationof the length.
 32. The catheter of claim 20 wherein the indicationdevice emits an audible indication of the length.
 33. The catheter ofclaim 20 wherein the indication device provides a tactile indication ofthe length.
 34. The catheter of claim 20 wherein the indication devicecomprises a plurality of holes and a movable detent, each hole beingconfigured to receive the detent, whereby adjusting the length moves thedetent from one hole to another hole.
 35. The catheter of claim 34wherein the reception of the detent in one of the holes provides atactile indication of the length of the interventional element.
 36. Thecatheter of claim 20 wherein the actuator comprises a ratchet mechanismthat allows adjustment of the length in a first direction and preventsadjustment of the length in a second direction.
 37. A stent deliverycatheter comprising: an elongated flexible shaft having distal andproximal ends; a stent releasably mounted at the distal end, adeployable portion of the stent being releasable from the catheter toassume an expanded configuration, the deployable portion having alength; an actuator at the proximal end for controlling the length ofthe deployable portion; and an indication device on the catheter forindicating the length of the deployable portion.
 38. The catheter ofclaim 37 wherein the actuator is movable through a distance correlatedwith the length.
 39. The catheter of claim 37 wherein the actuator ismovable through a stroke, each stroke of the actuator adjusting thelength a predetermined amount.
 40. The catheter of claim 39 wherein thestent comprises a plurality of stent segments, and the strokecorresponds to a segment length of one of the stent segments.
 41. Thecatheter of claim 37 wherein the indication device comprises a stop thatlimits the movement of the actuator.
 42. The catheter of claim 37wherein the indication device comprises a sensor for detecting thelength of the interventional element.
 43. The catheter of claim 42wherein the sensor is disposed near a distal end of the shaft, thesensor being coupled to an indicator at the proximal end.
 44. Thecatheter of claim 42 wherein the sensor is optical
 45. The catheter ofclaim 42 wherein the sensor is magnetic.
 46. The catheter of claim 42further comprising a display associated with the sensor for displayingan indication of the length.
 47. The catheter of claim 37 wherein theindication device provides a visual indication of the length.
 48. Thecatheter of claim 37 wherein the indication device emits an audibleindication of the length.
 49. The catheter of claim 37 wherein theindication device provides a tactile indication of the length.
 50. Thecatheter of claim 37 wherein the indication device comprises a pluralityof holes and a movable detent, each hole being configured to receive thedetent, whereby adjusting the length moves the detent from one hole toanother hole.
 51. The catheter of claim 50 wherein the reception of thedetent in one of the holes provides a tactile indication of the lengthof the interventional element.
 52. The catheter of claim 37 wherein theactuator comprises a ratchet mechanism that allows adjustment of thelength in a first direction and prevents adjustment of the length in asecond direction.
 53. The catheter of claim 37 wherein the stentcomprises a plurality of separable stent segments.
 54. The catheter ofclaim 53 wherein the catheter further comprises a sheath slidablerelative to the stent segments for selectively covering a first portionof the stent segment and exposing a second portion of the stentsegments.
 55. The catheter of claim 54 wherein the actuator moves thesheath relative to the stent segments.
 56. The catheter of claim 53wherein the actuator is further adapted to axially separate a firststent segment from a second stent segment prior to expansion thereof.57. The catheter of claim 56 wherein the actuator is adapted to separatethe first and second stent segments by a predetermined distance.
 58. Thecatheter of claim 56 wherein the actuator has a first position forcontrolling the number of stent segments in the deployable portion and asecond position for controlling the separation between the first andsecond stent segments.
 59. The catheter of claim 53 wherein theindication device indicates a number of stent segments in the deployableportion.
 60. The catheter of claim 37 wherein an undeployed portion ofthe stent remains on the catheter after the deployable portion isreleased from the catheter, further comprising an indication device forindicating the length of the undeployed portion.
 61. A method of usingan interventional catheter at a target site in a patient's body, themethod comprising: positioning an interventional element of theinterventional catheter near the target site, a proximal portion of theinterventional catheter being disposed outside the patient's body;adjusting a working length of the interventional element with theinterventional element remaining positioned in the patient's body;receiving from the proximal portion of the interventional catheter anindication of the working length; and after receiving the indication,deploying the interventional element.
 62. The method of claim 61 whereinthe interventional element comprises a balloon, and adjusting theworking length comprises constraining a first portion of the balloonfrom expansion while leaving a second portion of the balloonunconstrained from expansion.
 63. The method of claim 62 whereinconstraining comprises covering the first portion of the balloon by asheath movably disposed on the interventional catheter.
 64. The methodof claim 63 wherein the sheath is coupled to an indicator, theindication of working length being received from the indicator, whereinmoving the sheath changes the indication received from the indicator.65. The method of claim 62 wherein the indication of the working lengthcomprises an indication of the length of the second portion.
 66. Themethod of claim 61 wherein receiving the indication of working lengthcomprises observing a visual indication.
 67. The method of claim 66wherein the visual indication comprises one or more indicia displayed onthe proximal portion of the interventional catheter.
 68. The method ofclaim 61 wherein receiving the indication of working length compriseshearing an audible indication.
 69. The method of claim 61 whereinreceiving the indication of working length comprises feeling a tactileindication.
 70. The method of claim 69 wherein the tactile indication isreceived from a detent engaging a detent receiving structure associatedwith the interventional catheter.
 71. The method of claim 61 furthercomprising, after deploying the interventional element: positioning theinterventional element near a second target site; adjusting the workinglength of the interventional element to a second working length;receiving from the interventional catheter a second indication of thesecond working length; and after receiving the second indication,re-deploying the interventional element.
 72. A method of deploying astent at a target site in a patient's body, the method comprising:positioning a distal end of a delivery catheter near the target site,the stent being releasably coupled to the distal end, a proximal portionof the delivery catheter being disposed outside the patient's body;adjusting the length of a deployable portion of the stent with thedelivery catheter positioned in the patient's body; receiving anindication of the length from the proximal portion of the deliverycatheter; and after receiving the indication, deploying the deployableportion of the stent at the target site.
 73. The method of claim 72wherein adjusting the length of the deployable portion comprises movingan actuator associated with the proximal portion of the deliverycatheter through a distance correlated with the length.
 74. The methodof claim 73 wherein the actuator is movable through a stroke, eachstroke of the actuator adjusting the length a predetermined amount. 75.The method of claim 74 wherein the stent comprises a plurality of stentsegments, and the stroke corresponds to a segment length of one of thestent segments.
 76. The method of claim 73 wherein the indication devicecomprises a stop that limits the movement of the actuator.
 77. Thecatheter of claim 72 wherein the indication of the length is receivedfrom an output device associated with the proximal end of the catheter.78. The method of claim 77 wherein the output device is coupled to asensor, the method further comprising detecting the length with thesensor.
 79. The method of claim 78 wherein the sensor is disposed nearthe distal end of the delivery catheter.
 80. The method of claim 78wherein the sensor optically detects the working length.
 81. The methodof claim 78 wherein the sensor magnetically detects the working length.82. The method of claim 72 wherein receiving the indication of thelength comprises observing a visual indication.
 83. The method of claim82 wherein the visual indication comprises indicia displayed on theproximal portion of the delivery catheter.
 84. The method of claim 72wherein receiving the indication of length comprises hearing an audibleindication.
 85. The method of claim 72 wherein receiving the indicationof length comprises feeling a tactile indication.
 86. The method ofclaim 85 wherein the tactile indication is received from a detentengaging a detent receiving structure associated with the deliverycatheter.
 87. The method of claim 72 wherein adjusting the lengthcomprises moving a ratchet mechanism to adjust the length in a firstdirection, the ratchet preventing adjustment of the length in a seconddirection.
 88. The method of claim 72 wherein the stent comprises aplurality of separable stent segments and adjusting the length comprisesconstraining at least a first stent segment from expansion while leavingat least a second stent segment unconstrained from expansion.
 89. Themethod of claim 88 wherein adjusting the length comprises moving asheath relative to the stent segments for selectively covering the firststent segment and exposing the second stent segment.
 90. The method ofclaim 88 wherein the indication is correlated with the number of stentsegments.
 91. The method of claim 89 wherein the indication iscorrelated with movement of the sheath relative to the stent.
 92. Themethod of claim 88 further comprising axially separating the first stentsegment from the second stent segment prior to expansion thereof. 93.The method of claim 92 further comprising moving the actuator to a firstposition for controlling the number of stent segments in the deployableportion and moving the actuator to a second position for controlling theseparation between the first and second stent segments.